Nowadays, many electronic devices are developed toward minimization, portability and high performance. Consequently, the electronic components within these electronic devices must have high power or high integration level. During operation of the electronic devices, the electronic components may generate energy in the form of heat, which is readily accumulated and difficult to dissipate away. If no proper heat-dissipating mechanism is provided to transfer enough heat to the ambient air, the elevated operating temperature may result in damage of the electronic components, a breakdown of the whole electronic device or reduced operation efficiency. Therefore, it is important to dissipate the heat from the electronic components and control the temperature of the electronic device.
Generally, the heat-dissipating mechanisms used in the electronic device are divided into an active heat-dissipating mechanism and a passive heat-dissipating mechanism.
In accordance with the active heat-dissipating mechanism, an axial-flow fan or a blower is disposed within the electronic device to result in a relatively higher capacity of airflow. Consequently, the heat generated by the electronic device can be effectively exhausted to the surroundings. However, during operation of the axial-flow fan, undesired noise is generated. In addition, the axial-flow fan has bulky volume. Moreover, since the service life of the axial-flow fan or the blower is not long, the axial-flow fan or the blower is not suitably used in the small-sized and portable electronic device to dissipate away heat.
In accordance with the passive heat-dissipating mechanism, heat pipes and/or fins are disposed within the electronic device. Through the heat pipes and/or fins, the heat generated by the electronic components of the electronic device is transferred to the casing of the electronic device. The heat is further transferred to the ambient air by natural convection. However, the heat-dissipating efficiency of the passive heat-dissipating mechanism is inferior to the active heat-dissipating mechanism. Moreover, for increasing the heat-dissipating efficiency of the passive heat-dissipating mechanism, the heat pipes and the fins should be made of high thermally-conductive material. Under this circumstance, the fabricating cost is increased and the material selection is restricted.
For solving the above drawbacks, some other heat-dissipating mechanisms using a piezoelectric actuator have been disclosed. The use of the piezoelectric actuator may drive vibration of blades to generate airflow.
FIG. 1 schematically illustrates a conventional heat-dissipating mechanism disclosed in U.S. Pat. No. 7,061,161, which is entitled “Small piezoelectric air pumps with unobstructed airflow”. FIG. 2 schematically illustrates a conventional heat-dissipating mechanism disclosed in U.S. Pat. No. 7,358,649, which claims priority from U.S. Pat. No. 7,061,161. In these disclosures, an end of a T-shaped blade is connected with a piezoelectric element. The piezoelectric element drives the other end of the T-shaped blade to vibrate up and down. Consequently, an airflow is provided to cool the electronic device.
FIG. 3 schematically illustrates a conventional heat-dissipating mechanism disclosed in U.S. Pat. No. 7,742,299, which is entitled “Piezo fans for cooling an electronic device”. In this embodiment, at least one piezo fan is disposed on a back side of a printed circuit board (PCB). During operation of the piezo fan, an airflow is generated to cool the PCB.
FIG. 4 schematically illustrates a conventional heat-dissipating mechanism disclosed in U.S. Patent Publication No. 20110014069, which is entitled “Piezoelectric fan device and cooling apparatus using the piezoelectric fan device”. A piezoelectric fan comprises a blade and an actuator. The piezoelectric fan is fixed on a support member. When a voltage provided by a power supply is applied to the actuator through the support member, the actuator drives the blade to vibrate. Consequently, an airflow is generated.
FIG. 5 schematically illustrates a conventional heat-dissipating mechanism disclosed in U.S. Patent Publication No. 20110150669, which is entitled “Non-propeller fan”. The both ends of a flexible membrane are fixed. By utilizing electromagnetic force to drive vibration of the flexible membrane, an airflow in a fixed direction is generated.
FIG. 6 schematically illustrates a conventional heat-dissipating mechanism disclosed in U.S. Pat. No. 7,793,709, which is entitled “Jet generating device and electronic apparatus”. A vibration plate is disposed within the housing. By the vibration plate, the housing is partitioned into an upper chamber and a lower chamber. A voice coil motor is disposed within the housing, and partially attached on the vibration plate. The voice coil motor may drive the vibration plate to vibrate. The sinusoidal vibration of the vibrating plate causes the volume in the upper chamber and the lower chamber to increase or decrease. The change of the volume in the upper chamber and the lower chamber causes the airflow to be ejected out from the nozzles.
Since the above conventional heat-dissipating mechanisms are capable of dissipating heat in a single direction, the airflow direction is restricted, and it is difficult to reduce the volume of the electronic device.
Therefore, there is a need of providing an improved heat-dissipating module in order to eliminate the drawbacks encountered from the prior art.